Carburetor icing-eliminating structure



May 16, 1967 A. E. BRENNEMAN CARBURETOR ICING-ELIMINATING STRUCTURE Filed Oct. 30. 1964 ALBERT E. BRENNEMAN mvzm'on v 1 fzfw ATTORNEY 3.319.944 CARBURETOR IClldG-ELIMlNATl-NG STRUCTURE Albert E. Brenneman, Middletown, N.J., assignor to Essa Research and Engineering Company, a corporation of Delaware Filed Oct. 30, 1964, Ser. No. 408,470 1 Claim. (Cl. 261-41) The present invention relates to an improvement in a carburetor icing-eliminating structure. It has particular application to carburetors in automotive engines and the like, particularly those which are subject to difiiculties in operation under conditions where ice forms in the carburetor.

In the prior art, numerous proposals have been made to eliminate difiiculties due to the formation of ice in carburetors, particularly in the carburetors of automotive engines. It is well known that under certain adverse atmospheric conditions such as conditions of high relative humidity and at temperatures a few degrees above freezing, for example temperatures from about 50 F. down to 32 F. or so, serious difliculties are often encountered in maintaining operation of automotive engines at an idling rate. Particular difliculties arise in idling or low speed operation prior to full warming up of the engine. Various proposals have been made to avoid such ditficulties, including modification of the gasoline or fuel itself, eg by incorporating anti-freeze compositions therein such as alcohols, glycols, amides, and other chemical materials which are mutually soluble, to some de ree, in both gaso line and Water. The present invention is designed, among other things, to make such changes in fuel composition unnecessary, by providing mechanical means for taking care of the icing situation.

In a conventional automotive carburetor, the structure comprises a main body or barrel through which a stream of air, which is to support combustion of the fuel, is ad mitted and which flows past a carburetion point. The carburetion point usually is in the form of a constricted area, such as a venturi, where pressure is reduced due to increased velocity of the air stream. Due to the reduction in .pressure at such constriction, fuel is drawn into this area and is sprayed or jetted into the air stream with which it mixes and is evaporated. The vapors and air form a combustible or explosive mixture. The resulting mixture then proceeds to the engine at a rate controlled by a throttle valve. When the throttle valve is reasonably wide open and engine operation has been started successfully, there maybe no trouble with icing as long as the motor is running rather rapidly. However, in idling an automotive engine under the unfavorable atmospheric conditions mentioned above, and particularly in idling such an engine which has not become thoroughly warmed, icing frequently occurs. With the engine running at greater than idling speed fuel is drawn into the air stream at the venturi. Evaporation of this fuel in the air stream tends to reduce the temperature to a point at which the moisture, which is included in the air stream, will form ice crystals on the carburetor throttle plate. These ice crystals or particles may accumulate and completely block the narrow semicircular or crescent-shaped passages around the throttle plate when the throttle plate is moved towards a closed position. Under idling conditions the United States Patent is drawn in against a closed valve.

throttle plate of a conventional carburetor is not closed but is nearly closed, so that only a thin stream of air-fuel mixture can pass .by the throttle. Only air, without fuel, goes around the throttle plate under idling conditions because suction at the venturi is too low to bring in appreciable quantities of fuel. It is under such conditions that the small ice crystals or particles may block completely, or almost completely, the flow of air around the throttle plate. The resulting engine stalling is very annoying and sometimes makes it impossible to operate the engine properly.

In the past, it has been a common expedient in conventional carburetors to provide for a small amount of fuel to bypass the throttle valve to keep an engine running at idling speed. A so-called idling jet is usually provided. By means of the idler fuel bypass a small stream of fuel, usually gasoline, is passed beyond or around the throttle plate to keep the engine running. This bypassed stream of fuel is adequate for idling, provided enough air also gets past the throttle plate to provide for combustion of the idler fuel. Under the ice-forming conditions mentioned above, however, air does not flow around the carburetor throttle plate in sufiicient quantity to produce a good combustible mixture. As a result, with fuel which enters the engine .by the idler bypass, with no air or only a very limited quantity of air, too rich a mixture results and the engine will be starved for air and will cease to function because of the incombustible mixture presented to it.

In the prior art, various suggestions have been made that air might be let in downstream of the throttle valve by operation of spring valves and the like under highsuction conditions. Thus, in U.S. Patent 1,290,508, there is disclosed a carburetor in which an auxiliary air port is provided, the supply of auxiliary air entering the carburetor downstream of the throttle plate. The stream, however, is controlled by the vacuum in the engine manifold, as well as by a setting of the throttle plate. In this case, the auxiliary air valve appears to open only at rather high suction conditions and is not particularly adapted to purposes of the persent invention, which are concerned with idling and starting at low speeds.

Another example is given in U.S. Patent 2,699,157, wherein air from an upper part of a downdraft carburetor This valve, when opened against the force of the spring, may permit further air flow to the carburetor. Here again, the purpose of the present invention is not achieved because the returning air, or at least part of it, reenters the carburetor ahead of the throttle plate; and, moreover, the force to overcome the spring which normally holds the bypass in closed position often would not be available under the circumstances or conditions for which applicants device is designed.

Still another arrangement is shown in U.S. Patent 1,250,657, wherein air from the outside is let into the carburetor downstream of the throttle valve. This has the disadvantage, however, that the incoming air is not under control of the choke valve and this interferes in many cases with proper starting of the engine.

In U.S. Patent 1,944,397, an arrangement is shown wherein air may be bypassed downstream of the throttle valve, but under control of a light spring and valve by means of which engine idling could not be maintained.

Apparently the idling speed of the engine in this case would close off the bypass.

The present invention is different from all these in that it provides an unimpeded but closely controlled stream of air which is under direct control of the choke valve, but which re-enters the carburetor downstream of the throttle valve where icing occurs and therefore provides a definite and controlled air supply stream which will support combustion of idling proportions of fuel which also may be bypassed beyond the throttle valve.

While the invention takes several forms, it will be more fully understood by reference to the specific embodiment thereof which will next be described.

Referring to the accompanying drawing, wherein a preferred embodiment of the invention is shown, a structure is shown comprising a main carburetor barrel or body member 11. This is of conventional type and may vary in shape and relative dimensions, etc. As shown, the body 11 comprises a short cylindrical upper section 13 through which air is admitted to a restricted or venturi section 15 where mixing with fuel occurs. Below the venturi section is another short cylindrical section 17. The carburetor barrel has a bottom flange 19 by means of which it may be secured to an intake line or manifold 21, as in a conventional automobile engine. The line or manifold 21 has a fiange 23 to which bolts or studs 25 passing through flange 19 of the carburetor may be secured. A gasket 27 of usual type is clamped between the flanges.

The upper cylindrical section 11 contains the choke valve plate 29 mounted off-center on a transverse axle 31 which is pivotally mounted in the carburetor barrel. This valve is of conventional type and is operated by automatic or manual means,.not shown, as is well known in the art.

Into the venturi section 15 a tubular duct or jet element 33 is fitted. This tube connects to the fuel supply of conventional type, not shown. Due to reduced pressure at the venturi constriction, fuel such as gasoline is drawn into the center of the venturi mixing zone as the air stream flows througi. In the lower cylindrical section 17, the throttle valve plate 41 is mounted on rotatable shaft element 43. Operating mechanism, not shown, may be of any conventional type.

When the throttle valve 41 is closed or nearly so, the airflow through the venturi is usually too low to draw fuel in any appreciable quantity through the jet or duct 33. Hence a more or less conventional idling fuel bypass 51 is provided. This bypass is connected to the fuel supply in any conventional manner, not shown, as is well understood in the art. It is led into theside of the carburetor section 17 below the throttle plate 41. A needle valve adjustment preferably is provided between the conical seat 53 and the pointed rotatable screw 55 provided with a knurled head 57 for adjustment.

The carburetor parts so far described are more or less conventional. The carburetor shown is of the popular downdraft type but it will be understood that it can be oriented to any desired position or inverted for upfiow operation with suitable changes in connection to fuel and air supply, etc.

Under atmospheric conditions of highrelative humidity and moderately cool temperatures, carburetor icing commonly occurs. It is due in large part to the cooling effect of fuel vaporization in the venturi section when, after starting, the engine runs fast enough to draw fuel into the venturi. In a carburetor of the type shown, ice forms under such conditions in the narrow cresentshaped passages around the nearly closed throttle plate 41, as indicated at 61, 63. This icing can and often does close thin passages so fully that the engine will stall repeatedly, particularly during warm-up. Stalling under these conditions is not due to lack of fuel, since fuel is being bypassed around the throttle plate. It is due, rather, to a deficiency in air supply since insufiicient air for a good combustible mixture flows around the edges of the throttle plate. This deficiency is due to the ice. As a result, the engine will frequently become air starved.

By use of substantial amounts of anti-freeze materials, such as alcohol, in the fuel, icing may be prevented in large measure. Their ingredients, however, add considerably to the cost of gasoline.

According to the present invention, a small and closely controlled air supply is brought around the throttle plate and outside the main barrel of the carburetor by means of a bypass line 71. The upper end 73 of this line is connected to the barrel below the choke valve, so that total airflow through the carburetor is still under choke valve control. The lower end 75 connects to the lower section 17 of the carburetor below the throttle valve. It is provided with a conical valve seat 77, with Which the conical point 79 of a needle valve cooperates to obtain as careful an adjustment of airflow as may be desired. The needle valve has a knurled head 81 for manual adjustment.

The amount of air flowing through the bypass line 71 may be adjusted to prevent engine stalling due to air stoppage at the throttle plate and thereby to prevent air deficiency in the mixture which reaches the engine. At the same time, the rate of airflow through the bypass line is adjusted and controlled so that it will not substantially alter the overall fuel-air ratio of the mixture at the venturi, i.e. it does not substantially alter the carburetion, during normal operating conditions at higher than idling speeds. Obviously, by means of the structure described, the bypassed air may be adjusted as desired to match the idler fuel passing through line 51 so as to avoid unsatisfactory fuel mixtures, either too rich or too lean.

In operation, the throttle plate will be completely closed for idling so that all idler air is supplied through the bypass line. Then if the throttle plate is frozen shut with ice, it does not make any difference. Otherwise, if the throttle plate were open slightly, icing would upset the air-fuel balance for smooth idling. After the engine is fully warmed up, ice of course disappears but the necessary air for idling is still supplied through the bypass.

It will be understood that certain variations and modifications may be made within the spirit of the invention, as will be apparent to those skilled in the art. It is intended to cover such variations and modifications as broadly as the prior art properly permits, by the claim which follows.

\Vhat is claimed is:

In a carburetor for a gasoline engine the combination which comprises:

(a) a main curburetor barrel having upper and lower ends,

(b) a choke valve across the upper end of said barrel,

(c) a throttle valve near the lower end of said barrel,

(d) a venturi constricted fuel and air mixing zone in an intermediate position between said choke valve and said throttle valve,

(e) a main fuel line leading to and terminating in said zone,

(f) an idle fuel by-pass line for supplying fuel below said throttle valve, said fuel by-pass line having an outlet to said main carburetor barrel at a point just below said throttle valve,

(g) an air by-pass line for supplying fuel-free air below said throttle valve when said throttle valve is in a closed condition, said air by-pass line being connected from a point on said carburetor barrel below said choke valve and above said venturi zone and main fuel line to a point on said barrel below said throttle valve, said last point being diametrically opposite and somewhat below the outlet of said fuel by-pass line, and

(h) needle valve adjusting means located on the lower most extremity of said air by-pass line for positively and accurately adjusting the air flow from said air by-pass line, said adjusting means including a valve body having a comically shaped seat and an adjustable valve stem having a matching conically shaped end, said seat and said valve stem being so disposed in said air by-pass line so as to insure accurate adjustment of fuel-free air flow from said air by-pass line into said carburetor barrel substantially opposite the outlet of said fuel by-pass line.

References Cited by the Examiner UNITED STATES PATENTS 2,376,228 5/1945 Brown 261-56 X 5 3,151,604 10/1964 Walker et a1 26141 HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner. 

